Russia launched new missile strikes on the Odesa region raising fresh doubts about plans to restart grain shipments from Ukrainian ports this week.

The UN insisted plan on re-opening three ports were going ahead despite missile strikes at the weekend but the statement was followed by a further attack early on Tuesday.

The US said it was exploring other options to bring 20m tonnes of grain stored ready for export but admitted that shipments from Baltic Sea ports remained the best option to prevent a global food crisis.

Russia has insisted that there was nothing in the deal signed on Friday that stopped it from attacking military targets in Ukraine

It claimed to have destroyed Ukrainian missile and artillery depots on Monday. Ukraine said Russia hit port infrastructure in the Mykolaiv region while homes were hit in coastal villages near Odesa.

“We want to make sure that all conditions are right for the safe travel of ships,” said the spokesman for UN Secretary-General Antonio Guterres on Monday.

“Anything that’s not commensurate with that is, of course, not helpful for the success of this initiative… we want all sides, as the Secretary-General made clear on Saturday, to fully implement what they have agreed to.”

TradeWinds reported on Monday that insurers are ready to support shipowner clients but only after a safe passage for bulker carriers has been arranged. The UK government has also been encouraging the London market to step in.

The US said that preparations were continuing with the plan to prepare three ports over the next fortnight despite the “brazen” missile attack by Russia 24 hours after the deal was signed in Istanbul.

“We all know that the most effective means and the largest-scale means by which to increase those exports will be through the Black Sea,” said State Department spokesman Ned Price on Monday.

Ukraine says that the first exports could start later this week from the port of Chernomorsk with further exports following from Odesa and Yuzhny.

A joint coordination centre is being established in Istanbul.

Ukrainian officials have invited applications to move out the grain in convoys along de-mined safe sea corridors.